Ventilated rotary hook for sewing machines



Jl lly 22, 1941.

J. D. KARLE VENTILA'IED ROTARY-HOOK FOR S EWING MACHiNES Filed April 22. 1939 v gimme/"A101 10 I Joim, D. Karla Patented July 22, 1941 UNITED STATES PATENT OFFICE 1 zm'm.

VENTILATED ROTARY HOOK FOB SEWING MACHINES John D. Karle, Roselle Park, N. 1., aaslgnol' to The Singer Manufacturing Compa y. Elizabeth,

This invention relates to rotary hook and bobbin-thread-case devices complementary to ,the reciprocatory needle of a sewing machine in the formation of stitches. I

The present hook is an improvement upon the high-speed hooks shown in U. 8. Patents Nos. 1,179,371, 1,995,278, 2,085,699, and 2,154,403. Hooks of the type represented by the above cited patents are capable of successful operation at sewing speeds of 5000 stitches per minute and over. In the operation of high-speed hooks of the type in question, however, there has long been recognized a tendency for lint from the sewing threads and starch, clay or other filler materials from the work to accumulate in the rotary hook and, more particularly, in the narrow clearance space customarily provided behind the thread-case for passage of the needle-thread loops being cast about the thread-case by the operation of the rotary hook. This accumulation of lint and filler clogs the hook and requires to be cleaned out.

The present invention has for an object to provide a self-cleaningnon-clogging high-speed rotary hook and bobbin-thread-case combination,

i. e., one inwhich lint and filler will not accumulate and interfere 'with the sewing operation.

' Another object of the. invention is to provide a rotary hook and bobbin-thread-case device with an eflective'heat dissipator.

With the above and other objects in view, as will hereinafterappear, theinvention comprises the devices, combinations, and arrangements oi;

parts hereinafter set forth and illustrated in the accompanying drawingof a preferred embodiment of the invention, from which the several features of the invention and the advantages attained therebywiil be readily understood by those skilled in the art.

Qf theaccompanying drawing, Fig. 1 is a diametrical section of a'rotary hook and bobbinthread-case device embodying the invention. Fig. 2 is a front or open-face view of the rotary hook element from which the bobbin-threadcase has been removed. Fig. 3 is a rear view of the rotary hook element. Fig. 4 is a side elevation of the rotary hook element with the fan removed. Fig. 5 is a perspective view of the fan element of Figs. 1, 2 and 3, and Fig. 6 is a perspective view of a modified form of fan element.

The preferred embodiment of the invention illustrated comprises the usual bobbin-thread-case I having the rear face 2. front face I and peripheral bearing rib I which is stationarily Journaled in the internally grooved rim' 5 of the horizontal axis cup-shaped rotary hook member formed with a loop-taking beak 0 and other attributes of a conventional sewing machine rotary hook. The hook rim 0 is supported by three arms [the spoke portions I of which are radial to the hub 8 and lie in a plane normal to the hub axis. The arms I include the overhanging rim portions'lii, however, which carry the rim 5 and serve to offset the latter materially from the plane of the coplanar radial portions I of the rim-supporting arms I, thus aflording a large air-chamber ll between the back face 2 of the bobbin-thread-case and the plane of the inner faces of the radial portions I of the arms I.

In the specific embodiment of the invention illustrated, the air-chamber II is cylindrical and its axial depth is approximately .294 its diametral width. The ratio of axial depth to diametra] width is not critical provided it is in excess of one-eighth. The axial depth must be large enough in proportion to the diametral width to convert the heretofore narrow thread-clearance space into a free air circulatory chamber such that the fan-action of the arms I and particularly the rim-portions II thereof will be eflective in creating a condition of turbulence in the chamber II which clears the chamber of lint, filler, etc., and prevents clogging of the hook.-

It is also important that there be openings in the bottom or the hook-cup between'the spokelike portions I of the arms I. Air is freely admitted to the air-chamber ll through these back openings best shown in Figs. 3 and 4 and the presence of this large air-chamber in rear of the within and around the hook and prevents the deposit of lintand filler which would eventually clog the hook. This anti-clogging attribute of the present hook may be enhanced by installa- I tion of a fan II in the air-chamber ll. Such a fan may be of the centrifugal type shown in Fig. 5. or the inclined vane type shown in Fig. 6. A fan otseither type may be made from a single disk of sheet metal having a central hole through a tubular drawn hub-portion it which is to be press-fitted upon the portion II of the hook-hub 9 which projects into the air-chamber Ii. The centrifugal fan of Figs. 1, 2 and 3 has. radial edge-portions II bent to stand at right angles to the plane of the arms l1 which carry them. In the fan shown inFig. 6, the edge-portions iI are inclined to the arms II and hence have a tendency to blow air toward the hook rim and bobbin-thread-case to cool the parts. With either fan, air circulation is materially increased and this results in a clean and 0001 running hook.

The invention is not, however, to be understood as limited to the use of a fan in the hook air-chamber except insofar as the appended claims may require.

By projecting the hook-hub 9 into the airchamber 1 l, I not only provide a convenient support for an internal fan but also reduce the overall axial length of the hook-body and effect a material saving in the bar stock from which the hook is turned. I further am enabled to mount the hook-body on the hook-shaft with a minimum of overhang of the hook-raceway beyond the end of the shaft. running ofthe hook and minimizes the possibility of wabble of the stationary thread-case.

Having thus set forth the nature of the invention what I claim herein is:

1. The combination with a non-rotary bobbinthread-case having a peripheral bearing, of a cup-shaped rotary hook having a rim in which the bearing of said bobbin-thread-case is journaled, said hook rim having a plurality of radial supporting arms, there being an air-chamber between the back face of said bobbin-thread-case and the plane of the inner faces of the radial hook rim supporting arms, and a fan in said chamber having a greater number of blades than there are hook-rim-supporting arms;

2. The combination with a non-rotary bobbin- This condition favors true thread-case having a peripheral bearing, of a cup-shaped rotary hook having a rim in which the bearing of said bobbin-thread-case is journaled, said hook rim having a plurality of radial supporting. arms, there being an air-chamber between the back face of said bobbin-thread-case and theplane of the inner faces of the radial hook rim supporting arms, and a fan removably and replaceably secured in said chamber.

3. The combination with a non-rotary bobbinthread-case, of a cup-shaped rotary hook having a rim in which said bobbin-thread-case is peripherally journaled, said hook having a plurality of rim-supporting radial arms and a central hub, there being an air-chamber between the back face of said bobbin-thread-case and said radial arms into which said hub projects, and a fan mounted on said hub in said air-chamber.

4. The combination with a non-rotary bobbinthread-case, of a cup-shaped rotary hook having a rim in which said bobbin-thread-case is peripherally journaled, said hook having a plurality of rim-supporting radial arms and a central hub, there being an air-chamber between the back face of said bobbin-thread-case and said radial arms into which said hub projects. and a fan having blades and a tubular hub press-fitted upon said hook hub within said air-chamber.

5. A cup-shaped rotary hook having a rim, a hub, and a plurality of rim-supporting arms radiating from said hub, a stationary bobbinthread-case peripherally journaled in said hook rim, the axial depth of said hook cup being sufficient to provide a fan-encompassing air-chamher in rear of the bobbin-thread-case, and a fan in said air-chamber, within said book.

6. The combination with a non-rotary bobbinthread-case, of a horiztonal axis cup-shaped rotary hook having a rim in which said bobbinthread-case is journaled, said hook having an axial hub and a plurality of coplanar rim-supporting arms radiating from said hub, the rim of said hook being held offset from the plane of said arms by arm extensions normal to the plane of said arms proper and of a length exceeding one-fourth of the radial distance from the hookaxis to the ends of said co-planar arms to provide a non-clogging air-chamber behind the bobbin-thread-case.

7. A cup-shaped rotary hook having a rim, an internal air-chamber, and a hub projecting into said air-chamber.

8. A cup-shaped rotary hook having a rim, an internal air-chamber, a hub projecting into said air-chamber, and a fan mounted in said airchamber and surrounding said hub.

9. A cup-shaped rotary hook having a rim, an internal air-chamber, a hub projecting-into said air-chamber, and a fan mounted in said airchamber on the internally projecting end of said hub.

10. A cup-shaped rotary hook having a rim, an internal air-chamber, and a fan in said airchamber.

11. In a high-speed horizontal axis cupshaped rotary hook device of the type having a peripheral rim, a hub, and spaced radial'rimsupporting arms, and in which said rim is formed with a loop-taking hook and a raceway for a stationary bobbin-thread-case having a flat inner face, with a narrow' thread-clearance space between said inner face and the bottom of the hook-cup, the improvement which consists in deepening the hook-cup suiiiciently to convert the heretofore narrow thread-clearance space into a free air circulatory chamber whose axial depth is in excess of one-eighth of its diametral width.

12. In a high-speed horizontal axis cupshaped rotary hook device of the type having an axial hub and .a peripheral 'rim formed with a loop-taking hook and a raceway for a stationary cylindrical bobbin-thread case and joined to said hub by L-shaped arms having relatively long spoke-portions normal to the hook-axis and relatively short rim-portions parallel to the hookaxis to provide a narrow thread-clearance space between the plane of the inner faces of said spoke-portions and the inner face of said bobbin-thread-case, the improvement which consists in lengthening the rim-portions of said L-shaped arms sufliciently to convert the heretofore narrow thread-clearance space into a cylindrical free air circulatory chamber whose axial depth is in excess of one-eighth of its diametral width.

JOHN D. KARLE. 

